A control arrangement for use in controlling the electrical supply from a power supply unit including an internal capacitance. The control arrangement includes first and second magnetically linked inductors arranged in series with one another and defining a connection therebetween. Third and fourth magnetically linked inductors are each connected to the connection between the first and second inductors. A switch means provides switched connections between the third and fourth inductors and ground, and a controller is operable to control the operation of the switch means such that closing of a switch of the switch means results in the formation of an LCR circuit. The internal capacitance forms the capacitance of the LCR circuit and the third or fourth inductor form the inductance of the LCR circuit. The magnetic link between the third and fourth inductors allow an output to be generated from the other of the third and fourth inductors.